BONDED ASSEMBLIES AND METHODS FOR IMPROVING BOND STRENGTH OF A JOINT
Bonded assemblies and methods for improving the bond strength of a joint are provided. The joint may be formed between bonding surfaces of a first and a second component. The first component has a bonding surface adapted to be bonded to a bonding surface of a second component. A plurality of features may be formed in at least one of the bonding surfaces. The bonding surfaces are bonded together to form the joint. A bonding material layer between the bonding surfaces may form the joint or the first and second components may be co-cured to form the joint. A chemical and mechanical bond between the bonding surfaces is formed with the plurality of features forming the mechanical bond and increasing the bond area of the chemical bond. The features may be openings and/or protrusions such as holes, slots, and bosses.
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The present invention relates to bonded assemblies and methods for joint formation, and more particularly, to strengthened bonded assemblies and methods for improving bond strength in a joint.
BACKGROUNDThere are many applications and systems which involve the bonding of two or more components made of similar or dissimilar materials. The problems which are inherent in forming a joint between dissimilar materials are well known to those skilled in the art. In general, dissimilar materials, such as for example, a composite material and a metal material, often do not form good bonds with each other. The joints formed may be unsatisfactory. For example, in high performance products, a metallic material may be bonded to the surface of a composite. Composite materials have gained popularity in high-performance products that need to be lightweight, yet strong enough to withstand harsh loading and environmental conditions. Such high-performance products include aerospace components (tails, wings, fuselages, propellers, and fan blades), boat and scull hulls, kayaks, bicycle frames and automotive products as well as many other uses. Carbon fiber reinforced plastic is one such composite material but there are many types, typically comprised of reinforcing fibers in a resin matrix and referred to as fiber reinforced plastic.
One example of a part or component comprised of composite material is an airfoil of a gas turbine fan rotor, stator blade, or a propeller blade for an aircraft or wind turbine. A thin protective formed metallic sheet may be bonded to the leading edge of such a composite airfoil. However, such leading edges are subject to often severe environmental conditions such as erosion and foreign object damage which can lead to premature failure of the bondline, undesirably causing the joined components to separate.
Current bonding techniques typically involve elaborate surface preparation, however, they do not always work well with material combinations across different joint types and may not be able to withstand various loading and environmental factors without incurring unnecessary weight and cost. Moreover, the geometry of the components themselves may not provide adequate surface area to provide a good bond.
Accordingly, it is desirable to produce a strong and durable joint with a bond strength that can withstand various loading and environmental factors without incurring unnecessary weight and cost. In addition, it is desirable to produce a strong and durable joint with material combinations across different joint types as well as between similar materials in order to improve the dynamic life of a joint. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.
BRIEF SUMMARYThe present invention provides strengthened bonded assemblies and methods for improving the bond strength of a joint. In one embodiment, and by way of example only, a method for improving the bond strength of a joint between bonding surfaces of a first and a second component is disclosed. A first component may be provided having a bonding surface adapted to be bonded to a bonding surface of a second component. A plurality of features is formed in at least one of the bonding surfaces. The plurality of features may project or recede from the bonding surface. A bonding material layer is applied between the bonding surfaces and into the receded plurality of features and/or around the plurality of features to form a chemical and mechanical bond improving the strength of the joint between the components.
In accordance with another exemplary embodiment, an uncured fiber-reinforced composite material such as a prepreg may be applied over at least the bonding surface of the first component to form the second component comprised of the fiber-reinforced composite material which is then cured to form a co-cured joint. In this example, a separate bonding material layer is not necessary to form the co-cured joint.
Other independent features and advantages of the preferred embodiments will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.
The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and
The following detailed description of the invention is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description of the invention.
Referring to
Before proceeding further, it is noted that the components may each be comprised of any material such as but not limited to of any metal, composite, plastic, or ceramic material, or a combination thereof, that can be bonded to other materials such as, but not limited to, any metal, composite, plastic, or ceramic and combinations thereof. The bonding may be between components made of similar or dissimilar materials. As used herein, the term “component” refers to the material in any form. For example, the components can have a substantially rectangular form and shape (see, e.g.
Returning once again to the description, and with continued reference to
No matter where the plurality of features is formed, it will be appreciated that the plurality of features may be variously configured. For example, the plurality of features may comprise a plurality of openings (20a), protrusions (20b), or recesses (not shown) or the like, or a combination thereof. If the features comprise openings, the openings may comprise through holes, as shown most clearly in
The plurality of features may be integrally formed during component formation or after component formation by known methods. Such methods include laser drilling, electrical discharge machining (EDM), electrochemical machining (ECM), chemical etching, photolithography or a combination thereof, or the like. The plurality of features may be formed randomly or in repeating or non-repeating patterns. The type, density and size of the plurality of features in the bonding surface(s) 18 depends, for example, on the size of the component, the criticality of the bond (i.e. how well a joint failure can be tolerated), and the cost of forming such plurality of features. The depth and width of each feature have dimensions approximately within about two orders of magnitude of the bond layer thickness. However, it is to be appreciated that the size dimensions of each feature are not so limited.
The features are distributed in at least a portion of the bonding surfaces. In a preferred embodiment as shown in
A method for improving the bond strength of a joint 12 further includes the step of forming a chemical and mechanical bond between the bonding surfaces 18. In a particular preferred embodiment, this is accomplished by applying a bonding material between the respective bonding surfaces 18 and pressing the bonding surfaces 18 together. In those embodiments in which the plurality of features comprise openings 20a or recesses, this causes the bonding material to flow into the plurality of openings (See
The bonding material may be an adhesive such as an epoxy, urethane, acrylic, or the like as well known in the art. The choice of bonding material depends, for example, on the material of the components 14 and 16 to be bonded. While the various embodiments particularly refer to an adhesive bonding material, it will be understood that the invention is not so limited. For example, depending on the material of the components to be bonded, bonding materials may be comprised of metallic bonding materials (brazed or soldered joining), ceramic bonding materials (a fired material), or any other material acting as a bonding medium between components.
As was noted above, a chemical bond as well as a mechanical bond can be formed between the components to improve the bond strength of the joint 12 between the components 14 and 16. The geometry of the plurality of features in the bonding surface(s) 18 forms the mechanical bond. As less overlapping material is needed to form a strong bond, the size of the components 14 and 16 and the amount of component material needed to form a strong and durable joint 12 may be reduced.
Referring to
In the embodiment depicted in
Referring to
Referring to
During the co-curing process, the composite fibers in an epoxy matrix will flow in and around the plurality of features improving the bond strength of the co-cured joint between the components. The composite materials may have similar or dissimilar composite fiber.
From the foregoing, it is to be appreciated that the methods of the present invention provide a strong and durable joint with an improved bond strength that can withstand various loading and environmental factors to improve and increase the dynamic life of the joint and the bonded assembly. As less overlapping material is needed to form a strong and durable bond, the size of the components and the amount of component material needed to form a strong and durable joint may be reduced to decrease the weight and costs of the components and the bonded assembly.
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt to a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims
1. A method for improving the bond strength of a joint between bonding surfaces of a first and a second component, comprising the steps of:
- providing a first component having a bonding surface adapted to be bonded to a bonding surface of a second component, at least one of the bonding surfaces including a plurality of features; and
- bonding the bonding surfaces together to form a joint between the bonding surfaces;
- wherein the step of bonding comprises forming a chemical and mechanical bond between the bonding surfaces with the plurality of features forming the mechanical bond.
2. The method of claim 1, wherein the plurality of features comprise at least one of a plurality of protrusions, openings, or recesses, or a combination thereof.
3. The method of claim 2, wherein the plurality of features have size dimensions within about two orders of magnitude of the bonding layer thickness.
4. The method of claim 3, wherein the plurality of protrusions comprise at least one of a plurality of bosses or pins, or a combination thereof.
5. The method of claim 3, wherein the plurality of openings comprise at least one of a plurality of holes or slots, or a combination thereof.
6. The method of claim 3, wherein the plurality of features further comprise at least one undercut portion on at least one of the plurality of features.
7. The method of claim 1, wherein the step of bonding comprises the step of depositing bonding material between the bonding surfaces and pressing the bonding surfaces together to form a bonding material layer between the bonding surfaces.
8. The method of claim 7, wherein the step of depositing bonding material comprises depositing at least one of an adhesive material, a metallic bond material, or a ceramic bond material, or a combination thereof.
9. The method of claim 1, wherein the step of bonding the bonding surfaces together comprises:
- depositing a fiber-reinforced composite material over at least the bonding surface of the first component to form the second component comprised of the fiber-reinforced composite material; and
- curing the fiber-reinforced composite material to form a co-cured joint having improved bond strength with at least a portion of the fiber-reinforced composite material cured between the bonding surfaces.
10. The method of claim 9, wherein the first component comprises a metal sheet having two bonding surfaces and the second component comprises a composite airfoil, and the step of bonding comprises forming a bond between the two bonding surfaces of the metal sheet and the bonding surface of the composite airfoil to form a metallic leading edge on the composite airfoil.
11. A method of forming a joint having improved bond strength, the method comprising the steps of:
- providing a first component having a bonding surface with a plurality of features therein; and
- bonding a second component to the first component around said plurality of features to form the joint having improved bond strength through the formation of a chemical and mechanical bond.
12. The method of claim 11, wherein the plurality of features comprise at least one of a plurality of protrusions, openings, or recesses, or a combination thereof.
13. The method of claim 12, wherein the plurality of features have size dimensions within about two orders of magnitude of the bonding layer thickness.
14. The method of claim 13, wherein the plurality of protrusions comprise at least one of a plurality of bosses or pins, or a combination thereof.
15. The method of claim 13, wherein the plurality of openings comprise at least one of a plurality of holes or slots, or a combination thereof.
16. The method of claim 13, wherein the plurality of features further comprise an undercut portion on at least one of the plurality of features.
17. The method of claim 11, wherein the step of bonding the bonding surfaces together comprises the step of depositing bonding material between the bonding surfaces and pressing the bonding surfaces together to form a bonding material layer between the bonding surfaces.
18. The method of claim 11, wherein the step of bonding the second component comprises:
- depositing a fiber-reinforced composite material over at least the bonding surface of the first component to form the second component comprised of the fiber-reinforced composite material; and
- curing the fiber-reinforced composite material to form a co-cured joint with a chemical and mechanical bond between the first and second components.
19. A bonded assembly, comprising:
- a first component having a bonding surface;
- a second component having a bonding surface bonded to the bonding surface of the first component, at least one of the first or second components, or both, having a plurality of features formed in the respective bonding surface.
20. The bonded assembly of claim 19, further comprising a bonding material layer between the bonding surfaces of the first and second components to form a chemical and mechanical bond between the first and second components.
Type: Application
Filed: Sep 8, 2009
Publication Date: Mar 10, 2011
Applicant: HONEYWELL INTERNATIONAL INC. (Morristown, NJ)
Inventors: Raymond Gage (Phoenix, AZ), Adrian Allan (Phoenix, AZ)
Application Number: 12/555,633
International Classification: B32B 3/06 (20060101); B32B 37/14 (20060101);